Granite-Roll-Radar-Inspection (GRRI)

BIG ROLLS KEEP ON TURNING IN PAPER MILLS

The Granite Roll Radar Inspection (GRRI) method developed by Work Inc. improves the risk control of paper manufacturing machines:

IN WORK SAFETY

IN PRODUCTION OUTPUT

IN PRODUCTION CERTAINTY

The condition of your stone roll can be checked by the GRRI method. The survey is guick and it does not damage the stone. An inspection of one roll at the factory lasts only 2-4 hours. If necessary, it is possible to inspect the roll even while the roll is in the machine during a stoppage. A preliminary description of your roll is provided immediately after the survey.

THE GRRI IS A PIONEER METHOD

Geo-Work has been performing radar surveys since 1987. During these years approximately 350 stone rolls have been inspected. Our GRRI method is already being used regularly at numerous paper mills around the world. This method was developed in cooperation with Technology Development Centre, insurance companies, Valmet Paper Machine Inc., and the major paper mills in Finland. Geo-Work Inc. is continually investing in the further development of this method.

GET A CLEAR PICTURE OF THE STONE ROLL’S INNER STRUCTURE

The Geo-Work GRRI method pinpoints targets not visible to the human eye, such as cracks or other factors affecting the safe use of the roll. The final report received by the client includes a comprehensive graphical computer printout which shows the condition of the stone roll, and the location and size of any cracks. Every stone roll is individual; the first survey maps the condition of the roll and the structure of the stone material. The necessity for a follow-up survey is determined in discussions with the client. The results of the first survey are compared with material produced in later surveys. If changes are observed in later surveys, there is reason to suspect that a crack in the stone roll has begun to enlarge, which may result in the shattering of the stone.

ROLL SECTION IMAGE EXAMPLES

A granite roll is measured at forty to fifty stations depending on the size of the roll. The following are some examples of typical images.

Cracks:
An internal crack generates a parabolic reflection on the radar profile. The suspected roll area is scanned at every two inches to measure the length and direction of the crack.

Structures:
Granite is not homogeneous. The radar measurements are used to lay out the structural direction of the granite which possibly indicates the weakest direction.

Mineral Enclaves:
The radar measurement detects large deviating targets in the shell, such as quartz, feldspar, and biotite enclaves (agglomerations). These reflections are different from those formed by cracks. The enclaves do not compromise safety, however, they may cause the roll surface to crumble locally affecting paper quality and roll life.

Rust:
Strong radar reflections caused by rust penetrations are often found between the end flange and the granite body. They are wide near the surface and weaken toward the roll center, contrary to the reflections by cracks.

Filling:
Variations in urethane or concrete filling in the center hole are detected by the radar. Dampers, centering supports, filler pipes may also be located.

Axial Scan: There often is a step in the middle of the roll due to eccentric boring or sawing from each end. The shell thickness and variation in it are also measured.